FinFET device and method of forming same

ABSTRACT

A method includes forming a fin extending above an isolation region. A sacrificial gate stack having a first sidewall and a second sidewall opposite the first sidewall is formed over the fin. A first spacer is formed on the first sidewall of the sacrificial gate stack. A second spacer is formed on the second sidewall of the sacrificial gate stack. A patterned mask having an opening therein is formed over the sacrificial gate stack, the first spacer and the second spacer. The patterned mask extends along a top surface and a sidewall of the first spacer. The second spacer is exposed through the opening in the patterned mask. The fin is patterned using the patterned mask, the sacrificial gate stack, the first spacer and the second spacer as a combined mask to form a recess in the fin. A source/drain region is epitaxially grown in the recess.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application Ser.No. 62/491,716, filed on Apr. 28, 2017, entitled “FinFET Device andMethod of Forming Same,” which application is hereby incorporated hereinby reference in its entirety.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as, for example, personal computers, cell phones, digital cameras,and other electronic equipment. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductor layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. However, asthe minimum features sizes are reduced, additional problems arise thatshould be addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a perspective view of a fin field-effect transistor (“FinFET”)device in accordance with some embodiments.

FIG. 2 is a top view of a FinFET device in accordance with someembodiments.

FIGS. 3A-6A are cross-sectional views of intermediate stages in themanufacture of a FinFET device in accordance with some embodiments.

FIGS. 7A and 7B are cross-sectional views of intermediate stages in themanufacture of a FinFET device in accordance with some embodiments.

FIGS. 8A, 8B and 8C are cross-sectional views of intermediate stages inthe manufacture of a FinFET device in accordance with some embodiments.

FIGS. 9A, 9B and 9C are cross-sectional views of intermediate stages inthe manufacture of a FinFET device in accordance with some embodiments.

FIGS. 10A, 10B and 10C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 11A, 11B and 11C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 12A, 12B and 12C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 13A, 13B and 13C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 14A, 14B and 14C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 15A, 15B and 15C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 16A, 16B and 16C are cross-sectional views of intermediate stagesin the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 17A, 17B and 17C are cross-sectional views of a FinFET device inaccordance with some embodiments.

FIG. 18 is a top view of a FinFET device in accordance with someembodiments.

FIG. 19 is a top view of a FinFET device in accordance with someembodiments.

FIG. 20 is a top view of a FinFET device in accordance with someembodiments.

FIG. 21 is a flow diagram illustrating a method of forming a FinFETdevice in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments will be described with respect to a specific context,namely, a FinFET device and a method of forming the same. Variousembodiments discussed herein allow for forming a FinFET device that isconfigured to function as an electrostatic discharge (ESD) protectiondevice, and improving ESD protection proprieties of such an ESDprotection device. Various embodiments presented herein are discussed inthe context of a FinFET device formed using a gate-last process. Inother embodiments, a gate-first process may be used. Also, someembodiments contemplate aspects used in planar devices, such as planarFET devices.

FIG. 1 illustrates an example of a fin field-effect transistor (FinFET)10 in a three-dimensional view. The FinFET 10 comprises a fin 16 on asubstrate 12. The substrate 12 includes isolation regions 14, and thefin 16 protrudes above and from between neighboring isolation regions14. A gate dielectric 18 is along sidewalls and over a top surface ofthe fin 16, and a gate electrode 20 is over the gate dielectric 18.Source/drain regions 22 and 24 are disposed in opposite sides of the fin16 with respect to the gate dielectric 18 and gate electrode 20. TheFinFET 10 illustrated in FIG. 1 is provided for illustrative purposesonly and is not meant to limit the scope of the present disclosure. Assuch, many variations are possible, such as epitaxial source/drainregions, multiple fins, multilayer fins, etc.

FIG. 2 is a top view of a FinFET device 30 in accordance with someembodiments. In some embodiments, the FinFET device 30 may comprise aplurality of FinFETs, such as the FinFET 10 illustrated in FIG. 1,except each gate of the FinFET device 30 extends along sidewalls andover top surfaces of a plurality of fins. The FinFET device 30 comprisesa plurality of fin groups, such as fin groups 33 and 35. The fin group33 comprises a plurality of fins 32. The fin group 35 comprises aplurality of fins 34. In some embodiments, a distance D₃ betweenadjacent fins 32 of the fin group 33 may be substantially same as adistance D₄ between adjacent fins 34 of the fin group 35. In someembodiments, a distance D₅ between adjacent fin groups, such as the fingroup 33 and the fin group 35, may be greater than the distance D₃ andthe distance D₄. In some embodiments, the distance D₃ may be betweenabout 22 nm and about 26 nm. In some embodiments, the distance D₄ may bebetween about 22 nm and about 26 nm. In some embodiments, the distanceD₅ may be between about 180 nm and about 300 nm. In some embodiments, aratio D₃/D₅ may be between about 0.07 and about 0.15. In someembodiments, a ratio D₄/D₅ may be between about 0.07 and about 0.15. Bychoosing these values for the ratios D₃/D₅ and D₄/D₅, good isolationbetween the fin group 33 and the fin group 35 is achieved. In theillustrated embodiment, the FinFET device 30 comprises two fin groups,such as the fin groups 33 and 35. In other embodiments, the number offin groups may be less than two or more than two according to designrequirements of the FinFET device 30. In the illustrated embodiment,each of the fin groups 33 and 35 includes four fins. In otherembodiments, the number of fins in each of the fin groups 33 and 35 mayinclude less than four or more than four fins according to designrequirements of the FinFET device 30.

The FinFET device 30 further includes isolation regions 42, such thateach of the fins 32 and 34 protrudes above and from between neighboringisolation regions 42. The FinFET device 30 further includes a pluralityof gates 36 and a plurality of gates 38, such that each of the gates 36and 38 extends along sidewalls and over top surfaces of respective oneof the fin groups 33 and 35. In some embodiments, the gates 36 areactive gates and the gates 38 are dummy gates, such that the gates 38 donot function as gates to modulate conductivities of underlying channelregions of respective ones of the fins 32 and 34. Accordingly, the gates36 may also be referred to as active gates 36, and the gates 38 may alsobe referred to as dummy gates 38. In the illustrated embodiments, eachof the dummy gates 38 is interposed between adjacent pairs of the activegates 36. In other embodiments, the numbers of the active gates 36 andthe dummy gates 38, and their arrangement may vary according to designrequirements of the FinFET device 30. In some embodiments, a width W₁ ofthe active gates 36 is greater than a width W₂ of the dummy gates 38. Inother embodiments, a relative width of the dummy gates 38 with respectto the width of the active gates 36 may be altered according to designrequirements of the FinFET device 30. In some embodiments, the width W₁may be between about 150 nm and about 170 nm. In some embodiments, thewidth W₂ may be between about 100 nm and about 120 nm. In someembodiments, a ratio W₂/W₁ may be between about 0.58 and about 0.8. Insome embodiments, a distance D₁ between a dummy gate 38 and a nearestactive gate 36 is greater than a distance D₂ between adjacent activegates 36. In some embodiments, the distance D₁ may be between about 168nm and about 232 nm. In some embodiments, the distance D₂ may be betweenabout 60 nm and about 80 nm. In some embodiments, a ratio D₂/D₁ may bebetween about 0.25 and about 0.47. In other embodiments, variousdistances between gates 36 and 38 may be altered according to designrequirements of the FinFET device 30.

The FinFET device 30 further includes spacers 40 that extend alongsidewalls of the active gates 36 and sidewalls of the dummy gates 38. Insome embodiments, the spacers 40 have a width between about 5 nm andabout 10 nm. The FinFET device 30 comprises epitaxial source/drainregions 44 and 46, such that each of the active gates 36 is interposedbetween a respective one of the epitaxial source/drain regions 44 and arespective one of the epitaxial source drain/regions 46, and each of thedummy gates 38 is interposed between respective adjacent epitaxialsource/drain regions 44.

In some embodiments, each of the active gates 36 has an asymmetricsource/drain configuration, such that a respective epitaxialsource/drain region 46 is spaced apart from the active gate 36 by ashorter distance than a respective epitaxial source/drain region 44. Insome embodiments, each of the dummy gates 38 has a symmetricsource/drain configuration, such that both respective epitaxialsource/drain regions 44 are spaced apart from the dummy gate 38 by asame distance. In some embodiments, each of the epitaxial source/drainregions 46 is spaced apart from a respective active gate 36 by adistance D₇ that equals to the width of a respective spacer 40. In someembodiments, each of the epitaxial source/drain regions 44 is spacedapart from a respective dummy gate 38 and a respective active gate 36 bya distance D₆ that is greater than the distance D₇. In some embodiments,the distance D₆ may be between about 30 nm and about 40 nm. In someembodiments, the distance D₇ may be between about 5 nm and about 10 nm.In some embodiments, a ratio D₇/D₆ may be between about 0.12 and about0.33.

FIG. 2 further illustrates reference cross-sections that are used insubsequent figures. Cross-section A-A is along a longitudinal axis of anactive gate 36 of the FinFET device 30. Cross-section C-C is in a planethat is parallel to cross section A-A and is across an epitaxialsource/drain region 44. Cross-section B-B is perpendicular tocross-section A-A and is along a longitudinal axis of a fin 32 and in adirection of, for example, a current flow between the epitaxialsource/drain regions 44 and 46. Subsequent figures refer to thesereference cross-sections for clarity.

FIGS. 3A through 16A-C are cross-sectional views of intermediate stagesin the manufacturing of a FinFET device, such as the FinFET device 30illustrated in FIG. 2, in accordance with some embodiment. In FIGS. 3Athrough 16A-C, figures ending with an “A” designation are illustratedalong the reference cross-section A-A illustrated in FIG. 2; figuresending with a “B” designation are illustrated along the referencecross-section B-B illustrated in FIG. 2; and figures ending with a “C”designation are illustrated along the cross-section C-C illustrated inFIG. 2.

FIG. 3A illustrates a substrate 50. The substrate 50 may be asemiconductor substrate, such as a bulk semiconductor, asemiconductor-on-insulator (SOI) substrate, or the like, which may bedoped (e.g., with a p-type or an n-type dopant) or undoped. Thesubstrate 50 may be a wafer, such as a silicon wafer. Generally, an SOIsubstrate comprises a layer of a semiconductor material formed on aninsulator layer. The insulator layer may be, for example, a buried oxide(BOX) layer, a silicon oxide layer, or the like. The insulator layer isprovided on a substrate, typically a silicon or glass substrate. Othersubstrates, such as a multi-layered or gradient substrate may also beused. In some embodiments, the semiconductor material of the substrate50 may include silicon; germanium; a compound semiconductor includingsilicon carbide, gallium arsenic, gallium phosphide, indium phosphide,indium arsenide, and/or indium antimonide; an alloy semiconductorincluding SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP;combinations thereof; or the like.

The substrate 50 may further include integrated circuit devices (notshown). As one of ordinary skill in the art will recognize, a widevariety of integrated circuit devices such as transistors, diodes,capacitors, resistors, the like, or combinations thereof may be formedin and/or on the substrate 50 to generate the structural and functionalrequirements of the design for the resulting FinFET device. Theintegrated circuit devices may be formed using any suitable methods.

In some embodiments, appropriate wells (not shown) may be formed in thesubstrate 50. In some embodiments wherein the resulting FinFET device isan n-type device, the wells are p-wells. In some embodiments wherein theresulting FinFET device is a p-type device, the wells are n-wells. Inother embodiments, both p-wells and n-wells are formed in the substrate50. In some embodiments, p-type impurities are implanted into thesubstrate 50 to form the p-wells. The p-type impurities may be boron,BF₂, or the like, and may be implanted to a concentration of equal to orless than 10¹⁸ cm⁻³, such as in a range from about 10¹⁷ cm⁻³ to about10¹⁸ cm⁻³. In some embodiments, n-type impurities are implanted into thesubstrate 50 to form the n-wells. The n-type impurities may bephosphorus, arsenic, or the like, and may be implanted to aconcentration of equal to or less than 10¹⁸ cm⁻³, such as in a rangefrom about 10¹⁷ cm⁻³ to about 10¹⁸ cm⁻³. After implanting theappropriate impurities, an anneal may be performed on the substrate toactivate the p-type and n-type impurities that were implanted.

FIG. 3A further illustrates the formation of a mask 53 over thesubstrate 50. In some embodiments, the mask 53 may be used in asubsequent etching step to pattern the substrate 50 (see FIG. 4A). Asshown in FIG. 3A, the mask 53 may include a first mask layer 53A and asecond mask layer 53B. The first mask layer 53A may be a hard masklayer, may comprise silicon oxide, silicon nitride, silicon oxynitride,silicon carbide, silicon carbonitride, a combination thereof, or thelike, and may be formed using any suitable process, such as thermaloxidation, thermal nitridation, atomic layer deposition (ALD), physicalvapor deposition (PVD), chemical vapor deposition (CVD), a combinationthereof, or the like. The first mask layer 53A may be used to prevent orminimize etching of the substrate 50 underlying the first mask layer 53Ain the subsequent etch step (see FIG. 4A). The second mask layer 53B maycomprise photoresist, and in some embodiments, may be used to patternthe first mask layer 53A for use in the subsequent etching stepdiscussed above. The second mask layer 53B may be formed by using aspin-on technique and may be patterned using acceptable photolithographytechniques. In some embodiments, the mask 53 may comprise three or moremask layers.

FIG. 4A illustrates the formation of semiconductor strips 52 in thesubstrate 50. First, mask layers 53A and 53B may be patterned, whereopenings in mask layers 53A and 53B expose areas of the substrate 50where trenches 55 will be formed. Next, an etching process may beperformed, where the etching process creates the trenches 55 in thesubstrate 50 through the openings in the mask 53. The remaining portionsof the substrate 50 underlying a patterned mask 53 form a plurality ofsemiconductor strips 52. The etching may be any acceptable etch process,such as a reactive ion etch (RIE), neutral beam etch (NBE), the like, ora combination thereof. The etch process may be anisotropic. In someembodiments, after forming the semiconductor strips 52, any remainingportions of the mask 53 may be removed by any suitable process. In otherembodiments, portions of the mask 53, such as the first mask layer 53A,may remain over the semiconductor strips 52. In some embodiments, thesemiconductor strips 52 may have a height H₁ between about 45 nm andabout 65 nm, and a width W₃ between about 5 nm and about 7 nm.

In some embodiments, the semiconductor strips 52 may be formed by anysuitable method. For example, the semiconductor strips 52 may be formedusing one or more photolithography processes, includingdouble-patterning or multi-patterning processes. Generally,double-patterning or multi-patterning processes combine photolithographyand self-aligned processes, allowing patterns to be created that have,for example, pitches smaller than what is otherwise obtainable using asingle, direct photolithography process. For example, in one embodiment,a sacrificial layer is formed over the substrate 50 and patterned usinga photolithography process. Spacers are formed alongside the patternedsacrificial layer using a self-aligned process. The sacrificial layer isthen removed, and the remaining spacers, or mandrels, may then be usedto pattern the substrate to form the semiconductor strips 52.

FIG. 5A illustrates the formation of an insulation material in thetrenches 55 (see FIG. 4A) between neighboring semiconductor strips 52 toform isolation regions 54. The insulation material may be an oxide, suchas silicon oxide, a nitride, such as silicon nitride, the like, or acombination thereof, and may be formed by a high density plasma chemicalvapor deposition (HDP-CVD), a flowable CVD (FCVD) (e.g., a CVD-basedmaterial deposition in a remote plasma system and post curing to make itconvert to another material, such as an oxide), the like, or acombination thereof. Other insulation materials formed by any acceptableprocesses may be also used.

Furthermore, in some embodiments, the isolation regions 54 may include aconformal liner (not illustrated) formed on sidewalls and bottomsurfaces of the trenches 55 (see FIG. 4A) prior to the filling of thetrenches 55 with an insulation material of the isolation regions 54. Insome embodiments, the liner may comprise a semiconductor (e.g., silicon)nitride, a semiconductor (e.g., silicon) oxide, a thermal semiconductor(e.g., silicon) oxide, a semiconductor (e.g., silicon) oxynitride, apolymer, combinations thereof, or the like. The formation of the linermay include any suitable method, such as ALD, CVD, HDP-CVD, PVD, acombination thereof, or the like. In such embodiments, the liner mayprevent (or at least reduce) the diffusion of the semiconductor materialfrom the semiconductor strips 52 (e.g., Si and/or Ge) into thesurrounding isolation regions 54 during the subsequent annealing of theisolation regions 54. In some embodiments, after the insulation materialof the isolation regions 54 are deposited, an annealing process may beperformed on the insulation material of the isolation regions 54.

Referring further to FIG. 5A, a planarization process, such as achemical mechanical polishing (CMP), may remove any excess insulationmaterial of the isolation regions 54, such that top surfaces of theisolation regions 54 and top surfaces of the semiconductor strips 52 arecoplanar. In some embodiments where portions of the mask 53 remain overthe semiconductor strips 52 after forming the semiconductor strips 52,the CMP may also remove the remaining portions of the mask 53.

FIG. 6A illustrates the recessing of the isolation regions 54 to formShallow Trench Isolation (STI) regions 54. The isolation regions 54 arerecessed such that fins 56 protrude from between neighboring isolationregions 54. Further, the top surfaces of the isolation regions 54 mayhave a flat surface as illustrated, a convex surface, a concave surface(such as dishing), or a combination thereof. The top surfaces of theisolation regions 54 may be formed flat, convex, and/or concave by anappropriate etch. The isolation regions 54 may be recessed using anacceptable etching process, such as one that is selective to thematerial of the isolation regions 54. For example, a chemical oxideremoval using a CERTAS® etch, an Applied Materials SICONI tool, ordilute hydrofluoric (dHF) acid may be used.

A person having ordinary skill in the art will readily understand thatthe process described with respect to FIGS. 3A through 6A is just oneexample of how the fins 56 may be formed. In other embodiments, adielectric layer can be formed over a top surface of the substrate 50;trenches can be etched through the dielectric layer; homoepitaxialstructures can be epitaxially grown in the trenches; and the dielectriclayer can be recessed such that the homoepitaxial structures protrudefrom the dielectric layer to form fins. In yet other embodiments,heteroepitaxial structures can be used for the fins. For example, thesemiconductor strips 52 in FIG. 5A can be recessed, and one or morematerials different from the semiconductor strips 52 may be epitaxiallygrown in their place. In even further embodiments, a dielectric layercan be formed over a top surface of the substrate 50; trenches can beetched through the dielectric layer; heteroepitaxial structures can beepitaxially grown in the trenches using one or more materials differentfrom the substrate 50; and the dielectric layer can be recessed suchthat the heteroepitaxial structures protrude from the dielectric layerto form fins 56.

In some embodiments where homoepitaxial or heteroepitaxial structuresare epitaxially grown, the grown materials may be in situ doped duringgrowth. In other embodiments, homoepitaxial or heteroepitaxialstructures may be doped using, for example, ion implantation afterhomoepitaxial or heteroepitaxial structures are epitaxially grown. Invarious embodiments, the fins 56 may comprise silicon germanium(Si_(x)Ge_(1-x), where x can be between approximately 0 and 1), siliconcarbide, pure or substantially pure germanium, a III-V compoundsemiconductor, a II-VI compound semiconductor, or the like. For example,the available materials for forming III-V compound semiconductorinclude, but are not limited to, InAs, AlAs, GaAs, InP, GaN, InGaAs,InAlAs, GaSb, AlSb, AlP, GaP, and the like.

Referring to FIGS. 7A and 7B, a dielectric layer 58 is formed on thefins 56. The dielectric layer 58 may be, for example, silicon oxide,silicon nitride, a combination thereof, or the like, and may bedeposited (using, for example, ALD, CVD, PVD, a combination thereof, orthe like) or thermally grown (for example, using thermal oxidation, orthe like) according to acceptable techniques. A gate electrode layer 60is formed over the dielectric layer 58, and a mask 62 is formed over thegate electrode layer 60. In other embodiments, the dielectric layer 58may be omitted and the gate electrode layer 60 may be formed directly onthe fins 56. In some embodiments, the gate electrode layer 60 may bedeposited over the dielectric layer 58 and then planarized using, forexample, a CMP process. The mask 62 may be deposited over the gateelectrode layer 60. The gate electrode layer 60 may be made of, forexample, polysilicon, although other materials that have a high etchingselectivity with respect to the material of the isolation regions 54 mayalso be used. The mask 62 may include one or more layers of, forexample, silicon oxide, silicon nitride, silicon oxynitride, siliconcarbide, silicon carbonitride, a combination thereof, or the like, andmay be formed using any suitable process, such as thermal oxidation,thermal nitridation, ALD, PVD, CVD, a combination thereof, or the like.In an embodiment, the mask 62 comprises a first mask layer 62A formed ofsilicon oxide and a second mask layer 62B formed of silicon nitride. Insome embodiments, the first mask layer 62A may have a thickness betweenabout 15 nm and about 25 nm, and the second mask layer 62B may have athickness between about 50 nm and about 70 nm.

Referring to FIGS. 8A, 8B, and 8C, the mask 62 (see FIGS. 7A and 7B) maybe patterned using acceptable photolithography and etching techniques toform a patterned mask 72. The pattern of the patterned mask 72 istransferred to the gate electrode layer 60 by an acceptable etchingtechnique to form gates 70. Optionally, the pattern of the patternedmask 72 may similarly be transferred to the dielectric layer 58. Thepattern of the gates 70 cover respective channel regions of the fins 56while exposing source/drain regions of the fins 56. The gates 70 mayalso have a lengthwise direction substantially perpendicular to thelengthwise direction of respective fins 56, within process variations. Asize of the gates 70, and a pitch between the gates 70, may depend on aregion of a die in which the gates 70 are formed. In some embodiments,the gates 70 may have a larger size and a larger pitch when located in,for example, an input/output region of a die (e.g., where input/outputcircuitry is disposed) than when located in, for example, a logic regionof a die (e.g., where logic circuitry is disposed).

As described below in greater detail, the gates 70 are sacrificial gatesand are subsequently replaced by replacement gates. Accordingly, thegates 70 may also be referred to as sacrificial gates 70. In someembodiments, some of the replacement gates are active gates and some ofthe replacement gates are dummy gates. In some embodiments, thesacrificial gates 70A are replaced by active replacement gates and thesacrificial gates 70D are replaced by dummy replacement gates. In someembodiments, a width of the sacrificial gates 70D is less than a widthof the sacrificial gates 70A.

Referring further to FIGS. 8A, 8B, and 8C, lightly doped source/drain(LDD) regions 75 may be formed in the substrate 50. Similar to theimplantation process discussed above with reference to FIG. 3A,appropriate impurities are implanted into the fins to form the LDDregions 75. In some embodiments wherein the resulting FinFET device is ap-type device, p-type impurities are implanted into the fins 56 to formp-type LDD regions 75. In some embodiments wherein the resulting FinFETdevice is an n-type device, n-type impurities are implanted into thefins 56 to form n-type LDD regions 75. During the implantation of theLDD regions 75, the sacrificial gates 70 and the patterned mask 72 mayact as a mask to prevent (or at least reduce) dopants from implantinginto channel regions of the exposed fins 56. Thus, the LDD regions 75may be formed substantially in source/drain regions of the exposed fins56. The n-type impurities may be any of the n-type impurities previouslydiscussed, and the p-type impurities may be any of the p-type impuritiespreviously discussed. The LDD regions 75 may have a concentration ofimpurities between about 10¹⁵ cm⁻³ to about 10¹⁶ cm⁻³. After theimplantation process, an annealing process may be performed to activatethe implanted impurities.

Referring to FIGS. 9A, 9B, and 9C, a spacer layer 80 is formed onexposed surfaces of the sacrificial gates 70 (see FIG. 9B) and/or thedielectric layer 58 over the fins 56 (see FIG. 9C). Any suitable methodsof forming the spacer layer 80 may be used. In some embodiments, adeposition (such as CVD, ALD, or the like) may be used form the spacerlayer 80. In some embodiments, the spacer layer 80 may include one ormore layers of, for example, silicon nitride (SiN), silicon oxynitride,silicon carbonitride, silicon oxycarbonitride (SiOCN), a combinationthereof, or the like. In some embodiments, the spacer layer 80 maycomprise a first spacer layer 80A and a second spacer layer 80B over thefirst spacer layer 80A. In some embodiments, the first spacer layer 80Amay be formed of materials comprising Si, O, C, N, or combinationsthereof. In some embodiments, the second spacer layer 80B may be formedof materials comprising Si, O, C, N, or combinations thereof. In someembodiments, the first spacer layer 80A and the second spacer layer 80Bare formed of different materials. In some embodiment, the first spacerlayer 80A may comprise a first dielectric layer and a second dielectriclayer over the first dielectric layer. In some embodiments, the firstdielectric layer comprises a dielectric material having a k-valuebetween about 5 and about 7. In some embodiments, the first dielectriclayer has a thickness between about 1 nm and about 3 nm. In someembodiments, the second dielectric layer comprises a dielectric materialhaving a k-value between about 5 and about 7. In some embodiments, thesecond dielectric layer has a thickness between about 2 nm and about 4nm. In some embodiments, the second spacer layer 80B has a thicknessbetween about 6 nm and about 7 nm.

Referring to FIGS. 10A, 10B, and 10C, horizontal portions of the secondspacer layer 80B are removed, such that remaining vertical portions ofthe second spacer layer 80B form spacers 82. In some embodiments,horizontal portions of the second spacer layer 80B are removed using asuitable anisotropic etching process. In other embodiments, verticalportions of the second spacer layer 80B extending along sidewalls of thefins 56 may also be removed.

Referring to FIGS. 11A, 11B, and 11C, a patterned mask 74 is formed overthe sacrificial gates 70. In some embodiments, the patterned mask 74exposes regions of the fins 56 between adjacent sacrificial gates 70,where epitaxial source/drain regions of the resulting FinFET device aresubsequently formed. In some embodiments, the patterned mask 74 maycomprise a photoresist material and may be patterned using suitablephotolithography processes. In some embodiments, the patterned mask 74exposes entire regions of the fins 56 interposed between adjacentsacrificial gates 70A, and exposes portions of regions of the fins 56interposed between adjacent sacrificial gates 70A and 70D. The patternedmask 74 covers portions of the first spacer layer 8A that are exposedduring the forming of the spacers 82.

After forming the patterned mask 74, a patterning process is performedon the fins 56 to form recesses 76 and 78 in source/drain regions of thefins 56. In some embodiments, the patterning process may include asuitable anisotropic dry etching process, while using the patterned mask74, the sacrificial gates 70, the patterned mask 72, the spacers 82,and/or isolation regions 54 as a combined mask. The suitable anisotropicdry etching process may include a reactive ion etch (RIE), a neutralbeam etch (NBE), the like, or a combination thereof. In someembodiments, bottoms of the recesses 76 may be disposed below bottoms ofthe recesses 78. In some embodiments, a width of the recesses 76 isgreater than a width of the recesses 78. In some embodiments, using thepatterned mask 74 allows for reducing a width and a volume of therecesses 76, which improves growth properties of subsequently formedepitaxial source/drain regions. After forming the recesses 76 and 78,the patterned mask 74 is removed. In some embodiments where thepatterned mask 74 comprises a photoresist material, the patterned mask74 may be removed using an ashing process followed by a wet cleaningprocess. After the patterning process, each of the sacrificial gates 70has a sidewall spacer structure comprising an unremoved portion of thefirst spacer layer 80A and a spacer 82. In some embodiments, therecesses 76 have a depth D₈ (measured form top surfaces of respectivefins 56) between about 50 nm and about 70 nm. In some embodiments, therecesses 78 have a depth D₉ (measured form top surfaces of respectivefins 56) between about 45 nm and about 65 nm. In some embodiments, thedepth D₈ is greater than the depth D₉.

Referring to FIGS. 12A, 12B, and 12C, epitaxial source/drain regions 84and 86 are formed in the recesses 76 and 78 (see FIGS. 11A, 11B, and11C), respectively. In some embodiments, the epitaxial source/drainregions 84 and 86 are epitaxially grown in the recesses 76 and 78 usingmetal-organic CVD (MOCVD), molecular beam epitaxy (MBE), liquid phaseepitaxy (LPE), vapor phase epitaxy (VPE), selective epitaxial growth(SEG), a combination thereof, or the like. In some embodiments where theresulting FinFET device is an n-type device and the fins 56 are formedof silicon, the epitaxial source/drain regions 84 and 86 may includesilicon, SiC, SiCP, SiP, or the like. In some embodiments where theresulting FinFET device is a p-type device and the fins 56 are formed ofsilicon, the epitaxial source/drain regions 84 and 86 may include SiGe,SiGeB, Ge, GeSn, or the like. The epitaxial source/drain regions 84 and86 may have surfaces raised from respective surfaces of the fins 56 andmay have facets. In some embodiments, the epitaxial source/drain regions84 and 86 may extend past the fins 56 and into the semiconductor strips52. In some embodiments, a width of the epitaxial source/drain regions84 is greater than a width of the epitaxial source/drain regions 86. Insome embodiments, the epitaxial source/drain regions 84 have a greatervolume than the epitaxial source/drain regions 86. In some embodiments,the material of the epitaxial source/drain regions 84 and 86 may beimplanted with suitable dopants. In some embodiments, the implantationprocess is similar to the process used for forming the LLD regions 75 asdescribed above with reference to FIGS. 8A, 8B, and 8C, and thedescription is not repeated herein for the sake of brevity. In otherembodiments, the material of the epitaxial source/drain regions 84 and86 may be in situ doped during growth. In some embodiments, theepitaxial source/drain regions 84 may have a thickness T₁ between about50 nm and about 70 nm. In some embodiments, the epitaxial source/drainregions 86 may have a thickness T₂ between about 50 nm and about 70 nm.In some embodiments, the thickness T₁ may be greater than the thicknessT₂.

In the illustrated embodiments, each of the epitaxial source/drainregions 84 and each of the epitaxial source/drain regions 86 arephysically separate from other epitaxial source/drain regions 84 and 86,respectively. In other embodiments, adjacent epitaxial source/drainregions 84 and adjacent epitaxial source/drain regions 86 may be merged.Such an embodiment is depicted in FIGS. 17A, 17B, and 17C, whereadjacent epitaxial source/drain regions 84 are merged to form a commonepitaxial source/drain region 84.

Referring further to FIGS. 12A, 12B, and 12C, each of the sacrificialgates 70D has a symmetric arrangement of the epitaxial source/drainregions, such that each of the sacrificial gates 70D is separated fromadjacent epitaxial source/drain regions 84 by a same distance D₆ that isgreater than a sum of a thickness of the first spacer layer 80A and awidth of the spacers 82. In addition, each of the sacrificial gates 70Ahas an asymmetric arrangement of the epitaxial source/drain regions,such that each of the sacrificial gates 70A is separated from anadjacent epitaxial source/drain region 84 by the distance D₆, and froman adjacent epitaxial source/drain region 86 by the distance D₇ thatequals to a sum of the thickness of the first spacer layer 80A and thewidth of the spacers 82. Furthermore, regions of the fins 56 interposedbetween the epitaxial source/drain regions 84 and adjacent sacrificialgates 70 are covered by the first spacer layer 80A. In some embodiments,the first spacer layer 80A prevents the epitaxial source/drain regions84 from climbing up sidewalls of the spacers 82 and extending along thesidewalls of the spacers 82, which degrades the ESD protectioncapabilities of the resulting FinFET device. In some embodiments, byspacing apart the epitaxial source/drain regions 84 and adjacentsacrificial gates 70A, current punch through may be avoided in theresulting FinFET device. In some embodiments, the sidewalls of thespacers 82 and top surfaces of the first spacer layer 80A form an angleα. In some embodiments, the angle α is between about 90 degrees andabout 120 degrees.

Referring to FIGS. 13A, 13B, and 13C, an etch stop layer 87 and aninterlayer dielectric (ILD) 88 are deposited over the sacrificial gates70, and over the epitaxial source/drain regions 84 and 86. In anembodiment, the ILD 88 is a flowable film formed by a flowable CVD. Insome embodiments, the ILD 88 is formed of a dielectric material such asPhospho-Silicate Glass (PSG), Boro-Silicate Glass (BSG), Boron-DopedPhospho-Silicate Glass (BPSG), undoped Silicate Glass (USG), or thelike, and may be deposited by any suitable method, such as CVD, PECVD, aspin-on-glass process, a combination thereof, or the like. In someembodiments, the etch stop layer 87 is used as a stop layer whilepatterning the ILD 88 to form openings for subsequently formed contacts.Accordingly, a material for the etch stop layer 87 may be chosen suchthat the material of the etch stop layer 87 has a lower etch rate thanthe material of ILD 88. In some embodiments, a planarization process,such as a CMP, may be performed to level the top surface of ILD 88 withthe top surface of the patterned mask 72. After the planarizationprocess, the top surface of the patterned mask 72 is exposed through theILD 88. In other embodiments, the CMP may also remove a portion or anentirety of the patterned mask 72.

Referring to FIGS. 14A, 14B, and 14C, remaining portions of thepatterned mask 72 and the sacrificial gates 70 are removed to formrecesses 90 in the ILD 88. In some embodiments, the patterned mask 72and the sacrificial gates 70 are removed using one or more etchingsteps. Each of the recesses 90 exposes a channel region of a respectivefin 56. In some embodiments, the dielectric layer 58 may be used as anetch stop layer when the sacrificial gates 70 are etched. After removingthe sacrificial gates 70, the dielectric layer 58 may be also removed.

Referring to FIGS. 15A, 15B, and 15C, a gate dielectric layer 92 and agate electrode layer 94 are formed in the recesses 90 (see FIGS. 14A,14B, and 14C). The gate dielectric layer 92 is deposited conformally inthe recesses 90. In some embodiments, the gate dielectric layer 92comprises silicon oxide, silicon nitride, or multilayers thereof. Inother embodiments, the gate dielectric layer 92 includes a high-kdielectric material, and in these embodiments, the gate dielectric layer92 may have a k value greater than about 7.0, and may include a metaloxide or a silicate of Hf, Al, Zr, La, Mg, Ba, Ti, Pb, and combinationsthereof. The formation methods of the gate dielectric layer 92 mayinclude Molecular-Beam Deposition (MBD), ALD, PECVD, a combinationthereof, or the like. In some embodiments, the gate dielectric layer 92may have a thickness between about 3 nm and about 5 nm.

In some embodiments, an interfacial layer (not shown) may be formed overthe channels region of the fins 56 prior to forming the gate dielectriclayer 92, and the gate dielectric layer 92 is formed over theinterfacial layer. The interfacial layer helps buffer the subsequentlyformed high-k dielectric layer from the underlying semiconductormaterial. In some embodiments, the interfacial layer is a chemicalsilicon oxide, which may be formed of chemical reactions. For example, achemical oxide may be formed using deionized water+ozone (O₃),NH₄OH+H₂O₂+H₂O (APM), or other methods. Other embodiments may utilize adifferent material or processes (e.g., a thermal oxidation or adeposition process) for the interfacial layer. In some embodiments, theinterfacial layer may have a thickness between about 1 nm and about 3nm.

Next, the gate electrode layer 94 is deposited over the gate dielectriclayer 92 and fills the remaining portions of the recesses 90. The gateelectrode layer 94 may be a metal selected from a group of W, Cu, Ti,Ag, Al, TiAl, TiAlN, TaC, TaCN, TaSiN, Mn, Co, Pd, Ni, Re, Ir, Ru, Pt,and Zr. In some embodiments, the gate electrode layer 94 comprises ametal selected from a group of TiN, WN, TaN, and Ru. Metal alloys suchas Ti—Al, Ru—Ta, Ru—Zr, Pt—Ti, Co—Ni and Ni—Ta may be used and/or metalnitrides such as WN_(x), TiN_(x), MoN_(x), TaN_(x), and TaSi_(x)N_(y)may be used. The gate electrode layer 94 may be formed using a suitableprocess such as ALD, CVD, PVD, plating, or combinations thereof. In someembodiments, the gate electrode layer 94 may have a thickness betweenabout 100 nm and about 170 nm. After the filling of the recesses withthe gate electrode layer 94, a planarization process, such as a CMP, maybe performed to remove the excess portions of the gate dielectric layer92 and the gate electrode layer 94, which excess portions are over thetop surface of ILD 88. The resulting remaining portions of materials ofthe gate electrode layer 94 and the gate dielectric layer 92 thus formreplacement gates 96 of the resulting FinFET device. The replacementgates 96 that are disposed between adjacent epitaxial source/drainregions 84 are dummy replacement gates 96D, and the replacement gates 96that are disposed between epitaxial source/drain regions 84 and 86 areactive replacement gates 96A. As described below in greater detail,since the replacement gates 96D are dummy gates, contacts may not beformed to make an electrically contact to the dummy replacement gates96D.

In some embodiments, one or more work function layers (not shown) may beformed over the gate dielectric layer 92 prior to forming the gateelectrode layer 94, and the gate electrode layer 94 is formed over theone or more work function layers. In some embodiments, the one or morework function layers may comprise TaN, TiN, a combination thereof, orthe like, and may be formed using ALD, CVD, a combination thereof, orthe like. In some embodiments, the sacrificial gates 70 may remainrather than being replaced by the replacement gates 96.

Referring to FIGS. 16A, 16B, and 16C, an ILD 102 is deposited over theILD 88, contacts 104 are formed through the ILD 102 and the ILD 88, andcontacts 108 are formed through the ILD 102. In an embodiment, the ILD102 is formed using similar materials and methods as the ILD 88described above with reference to FIGS. 14A, 14B, and 14C, and thedescription is not repeated herein for the sake of brevity. In someembodiments, the ILD 102 and the ILD 88 are formed of a same material.In other embodiments, the ILD 102 and the ILD 88 are formed of differentmaterials.

Openings for the contacts 104 are formed through the ILDs 88 and 102,and the etch stop layer 87. Openings for the contacts 108 are formedthrough the ILD 102 and the etch stop layer 87. These openings may allbe formed simultaneously in a same process, or in separate processes.The openings may be formed using acceptable photolithography and etchingtechniques. A liner, such as a diffusion barrier layer, an adhesionlayer, or the like, and a conductive material are formed in theopenings. The liner may include titanium, titanium nitride, tantalum,tantalum nitride, or the like. The conductive material may be copper, acopper alloy, silver, gold, tungsten, aluminum, nickel, or the like. Aplanarization process, such as a CMP, may be performed to remove excessmaterials from a top surface of the ILD 102. The remaining liner andconductive material form contacts 104 and 108. An anneal process may beperformed to form a silicide (not shown) at the interface between theepitaxial source/drain regions 84 and 86 and the contacts 104,respectively. The contacts 104 are physically and electrically coupledto the epitaxial source/drain regions 84 and 86, and the contacts 108are physically and electrically coupled to the replacement gates 96. Insome embodiments, contacts are not formed to be physically andelectrically coupled to the dummy replacement gates 96D. While thecontacts 104 are depicted in FIG. 16B in a same cross-section as thecontacts 108, this depiction is for the purposes of illustration onlyand, in some embodiments, the contacts 104 may be disposed in adifferent cross-section from the contacts 108. In some embodiments, thecontacts 104 are spaced apart from nearest spacers 82 of dummyreplacement gates 96D by a distance D₁₀. In some embodiments, thedistance D₁₀ is between about 10 nm and about 25 nm.

FIGS. 17A, 17B, and 17C illustrate cross-sectional views of a FinFETdevice that is similar to the FinFET device illustrated in FIGS. 16A,16B, and 16C, with like elements labeled with like numerical references.In some embodiments, the FinFET device of FIGS. 17A, 17B, and 17C may beformed using similar materials and methods and FinFET device of FIGS.16A, 16B, and 16C described above with reference to FIGS. 3A-16C, andthe description is not repeated herein for the sake of brevity. In theillustrated embodiment, adjacent epitaxial source/drain regions 84 aremerged to form a common epitaxial source/drain region 84. In someembodiments, voids (not shown) may be formed below the common epitaxialsource/drain region 84, between the common epitaxial source/drain region84 and the isolation regions 54. In some embodiments, the voids arefilled with the material of the ILD 88. In the illustrated embodiment,the common epitaxial source/drain region 84 has a planar top surface. Inother embodiments, the common epitaxial source/drain region 84 may havea non-planar top surface.

FIG. 18 is a top view of a FinFET device 180 in accordance with someembodiments. The FinFET device 180 is similar to the FinFET device 30illustrated in FIG. 2, with like elements labeled with like numericalreferences. In the illustrated embodiments, adjacent epitaxialsource/drain regions 44 are merged to form common epitaxial source/drainregions 44 for the fin groups 33 and 35, and adjacent epitaxialsource/drain regions 46 are merged to form common epitaxial source/drainregions 46 for fin groups 33 and 35.

FIG. 19 is a top view of a FinFET device 190 in accordance with someembodiments. The FinFET device 190 is similar to the FinFET device 30illustrated in FIG. 2, with like elements labeled with like numericalreferences. In the illustrated embodiments, the FinFET device 190comprises the active gates 36 and the dummy gates 38 that extend overboth the fin group 33 and the fin group 35.

FIG. 20 is a top view of a FinFET device 200 in accordance with someembodiments. The FinFET device 200 is similar to the FinFET device 30illustrated in FIG. 2, with like elements labeled with like numericalreferences. In the illustrated embodiments, the FinFET device 200comprises the active gates 36 and the dummy gates 38 that extend overboth the fin group 33 and the fin group 35. Furthermore, the FinFETdevice 200 comprises individual epitaxial source/drain regions 44 and 46for each of the fins 32 and each of the fins 34.

FIG. 21 is a flow diagram illustrating a method 210 of forming a FinFETdevice in accordance with some embodiments. The method 210 starts withstep 212, where a substrate (such as the substrate 50 illustrated inFIG. 3A) is patterned to form fins (such as the fins 56 illustrated inFIG. 6A) as described above with reference to FIGS. 3A-6A. In step 214,sacrificial gate stacks (such as the sacrificial gates 70 illustrated inFIGS. 8A and 8B) are formed over the fins as described above withreference to FIGS. 7A, 7B, and 8A-8C. In step 216, spacers (such as thespacers 82 illustrated in FIG. 10B) are formed on sidewalls of thesacrificial gate stacks as described above with reference to FIGS.9A-10C. In step 218, a mask (such as the patterned mask 74 illustratedin FIGS. 11A and 11B) is formed over the sacrificial gate stacks and thespacers as described above with reference to FIGS. 11A-11C. In step 220,the fins are patterned using the sacrificial gate stacks, the spacersand the mask as a combined mask to form recesses (such as the recesses76 and 78 illustrated in FIGS. 11B and 11C) in the fins as describedabove with reference to FIGS. 11A-11C. In step 222, source/drain regions(such as the epitaxial source/drain regions 84 and 86 illustrated inFIGS. 12B and 12C) are epitaxially grown in the recesses as describedabove with reference to FIGS. 12A-12C. In step 224, replacement gatestacks (such as the replacement gates 96 illustrated in FIGS. 15A and15B) are formed over the fins as described above with reference to FIGS.13A-15C.

Various embodiments discussed herein allow for forming a FinFET device,which may function as an ESD protection device. Various embodimentsfurther allow for improving ESD protection proprieties, avoiding currentpunch through, improving growth properties of epitaxial source/drainregions, and preventing the epitaxial source/drain regions from climbingup along sidewalls of gate spacers during the epitaxial growth.

According to an embodiment, a method includes: forming a fin extendingabove an isolation region; forming a sacrificial gate stack over thefin, the sacrificial gate stack having a first sidewall and a secondsidewall opposite the first sidewall; forming a first spacer on thefirst sidewall of the sacrificial gate stack; forming a second spacer onthe second sidewall of the sacrificial gate stack; forming a patternedmask layer having an opening therein over the sacrificial gate stack,the first spacer and the second spacer, the patterned mask layerextending along a top surface and a sidewall of the first spacer, thesecond spacer being exposed through the opening in the patterned masklayer; patterning the fin using the patterned mask layer, thesacrificial gate stack, the first spacer and the second spacer as acombined mask to form a recess in the fin; and epitaxially growing asource/drain region in the recess. In an embodiment, forming the firstspacer and forming the second spacer includes: forming a first spacerlayer over a top surface and along the first sidewall and the secondsidewall of the sacrificial gate stack; forming a second spacer layerover the first spacer layer; and removing lateral portions of the secondspacer layer, remaining portions of the second spacer layer forming thefirst spacer and the second spacer. In an embodiment, the first spacerlayer and the second spacer layer comprise different materials. In anembodiment, the method further includes replacing the sacrificial gatestack with a replacement gate stack. In an embodiment, the replacementgate stack is an active gate stack. In an embodiment, the replacementgate stack is a dummy gate stack. In an embodiment, the source/drainregion and the fin comprise different semiconductor materials.

According to another embodiment, a method includes: patterning asubstrate to form trenches, the substrate comprising a firstsemiconductor material; filling trenches with a dielectric material toform isolation regions; etching the isolation regions to expose fins;forming a sacrificial gate stack along sidewalls and over top surfacesof the fins; depositing a first spacer layer along a sidewall and over atop surface of the sacrificial gate stack and over the top surfaces ofthe fins; depositing a second spacer layer over the first spacer layer;etching the second spacer layer to remove lateral portions of the secondspacer layer, remaining portions of the second spacer layer forming gatespacers; forming a patterned mask over the sacrificial gate stack andthe gate spacers, the patterned mask extending over at least a portionof the first spacer layer disposed over the top surfaces of the fins notbeing protected by at least one of the gate spacers; etching the firstspacer layer and the fins using the patterned mask, the sacrificial gatestack, and the gate spacers as a combined mask to form first recesses inthe fins; and filling the first recesses with a second semiconductormaterial to form source/drain regions in the first recesses. In anembodiment, the first spacer layer and the second spacer layer comprisedifferent materials. In an embodiment, the first semiconductor materialis different from the second semiconductor material. In an embodiment,the method further includes: forming a dielectric layer over thesource/drain regions and along the sidewalls of the sacrificial gatestack; removing the sacrificial gate stack form a second recess in thedielectric layer; and forming a replacement gate stack in the secondrecess. In an embodiment, the replacement gate stack is an active gatestack. In an embodiment, the replacement gate stack is a dummy gatestack. In an embodiment, the method further includes merging thesource/drain regions to form a common source/drain region for the fins.

According to yet another embodiment, a device includes: a fin over asubstrate; a gate stack along sidewalls and over a top surface of achannel region of the fin, the gate stack having a first sidewall and asecond sidewall opposite the second sidewall; a first gate spacerstructure along the first sidewall of the gate stack, the first gatespacer structure comprising a first gate spacer, a first portion of thefirst gate spacer extending along the first sidewall of the gate stack,a second portion of the first gate spacer extending laterally away fromthe first sidewall of the gate stack and over the top surface of thefin; a second gate spacer structure along the second sidewall of thegate stack, the second gate spacer structure comprising a second gatespacer, a first portion of the second gate spacer extending along thesecond sidewall of the gate stack, a second portion of the second gatespacer extending laterally away from the second sidewall of the gatestack and over the top surface of the fin, a width of the second portionof the second gate spacer being less than a width of the second portionof the first gate spacer; a first epitaxial region adjacent the firstgate spacer structure; and a second epitaxial region adjacent the secondgate spacer structure. In an embodiment, the first gate spacer structurefurther comprises a third gate spacer extending along a sidewall of thefirst portion of the first gate spacer. In an embodiment, the secondgate spacer structure further comprises a fourth gate spacer extendingalong a sidewall of the first portion of the second gate spacer, a widthof the fourth gate spacer being substantially equal to a width of thethird gate spacer. In an embodiment, a volume of the first epitaxialregion is greater than a volume of the second epitaxial region. In anembodiment, a width of the first epitaxial region is greater than awidth of the second epitaxial region. In an embodiment, a thickness ofthe first epitaxial region is greater than a thickness of the secondepitaxial region.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a fin extendingabove an isolation region; forming a sacrificial gate stack over thefin, the sacrificial gate stack having a first sidewall and a secondsidewall opposite the first sidewall; forming a first spacer on thefirst sidewall of the sacrificial gate stack; forming a second spacer onthe second sidewall of the sacrificial gate stack, wherein forming thefirst spacer and forming the second spacer comprises: forming a firstspacer layer over a top surface and along the first sidewall and thesecond sidewall of the sacrificial gate stack; forming a second spacerlayer over the first spacer layer; and removing lateral portions of thesecond spacer layer, remaining portions of the second spacer layerforming the first spacer and the second spacer; forming a patterned masklayer having an opening therein over the sacrificial gate stack, thefirst spacer and the second spacer, the patterned mask layer extendingalong a top surface and a sidewall of the first spacer, the secondspacer being exposed through the opening in the patterned mask layer;patterning the fin using the patterned mask layer, the sacrificial gatestack, the first spacer and the second spacer as a combined mask to forma recess in the fin; and epitaxially growing a source/drain region inthe recess.
 2. The method of claim 1, wherein the first spacer layer andthe second spacer layer comprise different materials.
 3. The method ofclaim 1, further comprising replacing the sacrificial gate stack with areplacement gate stack.
 4. The method of claim 3, wherein thereplacement gate stack is an active gate stack.
 5. The method of claim3, wherein the replacement gate stack is a dummy gate stack.
 6. Themethod of claim 1, wherein the source/drain region and the fin comprisedifferent semiconductor materials.
 7. The method of claim 1, wherein asidewall of the first spacer and a top surface of the first spacer layerform an angle between about 90 degrees and about 120 degrees.
 8. Amethod comprising: patterning a substrate to form trenches, thesubstrate comprising a first semiconductor material; filling trencheswith a dielectric material to form isolation regions; etching theisolation regions to expose fins; forming a sacrificial gate stack alongsidewalls and over top surfaces of the fins; depositing a first spacerlayer along a sidewall and over a top surface of the sacrificial gatestack and over the top surfaces of the fins; depositing a second spacerlayer over the first spacer layer; etching the second spacer layer toremove lateral portions of the second spacer layer, remaining portionsof the second spacer layer forming gate spacers; forming a patternedmask over the sacrificial gate stack and the gate spacers, the patternedmask extending over a portion of the first spacer layer disposed overthe top surfaces of the fins and not protected by the gate spacers;etching the first spacer layer and the fins using the patterned mask,the sacrificial gate stack, and the gate spacers as a combined mask toform first recesses in the fins; and filling the first recesses with asecond semiconductor material to form source/drain regions in the firstrecesses.
 9. The method of claim 8, wherein the first spacer layer andthe second spacer layer comprise different materials.
 10. The method ofclaim 8, wherein the first semiconductor material is different from thesecond semiconductor material.
 11. The method of claim 8, furthercomprising: forming a dielectric layer over the source/drain regions andalong the sidewalls of the sacrificial gate stack; removing thesacrificial gate stack form a second recess in the dielectric layer; andforming a replacement gate stack in the second recess.
 12. The method ofclaim 11, wherein the replacement gate stack is an active gate stack.13. The method of claim 11, wherein the replacement gate stack is adummy gate stack.
 14. The method of claim 11, further comprising mergingthe source/drain regions to form a common source/drain region for thefins.
 15. A method comprising: forming an isolation region over asubstrate; recessing the isolation region to expose a fin; forming afirst sacrificial gate stack over the fin, the first sacrificial gatestack having a first sidewall and a second sidewall opposite the firstsidewall; forming a second sacrificial gate stack over the fin, thesecond sacrificial gate stack having a third sidewall and a fourthsidewall opposite the third sidewall; forming a first spacer on thefirst sidewall of the first sacrificial gate stack; forming a secondspacer on the second sidewall of the first sacrificial gate stack;forming a third spacer on the third sidewall of the second sacrificialgate stack; forming a fourth spacer on the fourth sidewall of the secondsacrificial gate stack; forming a patterned mask layer over the firstsacrificial gate stack and the second sacrificial gate stack, thepatterned mask layer coving the first spacer, the second spacer and thethird spacer, the patterned mask layer exposing the fourth spacer;patterning the fin using the patterned mask layer, the first sacrificialgate stack, the second sacrificial gate stack, the first spacer, thesecond spacer, the third spacer and the fourth spacer as a combined maskto form a first recess and a second recess in the fin, the first recessbeing interposed between the first sacrificial gate stack and the secondsacrificial gate stack, the second sacrificial gate stack beinginterposed between the first recess and the second recess; epitaxiallygrowing a first source/drain region in the first recess; and epitaxiallygrowing a second source/drain region in the second recess.
 16. Themethod of claim 15, further comprising replacing the first sacrificialgate stack with a dummy replacement gate stack.
 17. The method of claim15, further comprising replacing the second sacrificial gate stack withan active replacement gate stack.
 18. The method of claim 15, wherein awidth of the first source/drain region is greater than a width of thesecond source/drain region.
 19. The method of claim 15, wherein thefirst source/drain region is spaced apart form the second sacrificialgate stack by a first distance, and wherein the second source/drainregion is spaced apart form the second sacrificial gate stack by asecond distance different from the first distance.
 20. The method ofclaim 19, wherein the first distance is greater than the seconddistance.